191. Diphtheria: etiology, pathogenesis, pathological anatomy. Complications, causes of death.

Diphtheria is an acute infectious disease characterized mainly by fibrinous inflammation in the focus of primary fixation of the pathogen and general intoxication associated with the absorption of exotoxin MB.

The causative agent of diphtheria is Corynebacterium diphteriae (diphtheria bacillus). The pathogenic properties of diphtheria bacillus are mainly associated with the release of exotoxin. It is the action of the toxin that determines the clinical manifestations of diphtheria. The toxigenic nature of diphtheria bacillus is determined by the presence of a bacteriophage infecting Corynebacteria and carrying genes that determine the production of the toxin.

Source of infection: 1) bacilli carriers 2) patients (to a lesser extent)

Pathogenesis: reproduction of diphtheria bacillus in the area of the entrance gate on the mucous membranes → exotoxin release:

a) suppression of respiratory cycle enzymes, changes in cholinergic processes, impaired synthesis of KA and their accumulation in tissues

b) epithelial necrosis, vascular paresis and impaired permeability, tissue edema and fibrinogen release from their bloodstream → fibrinogen coagulation under the action of tissue thromboplastin → fibrinous film on the surface of the damaged mucosa

c) effect on the cardiovascular system, adrenal glands, nervous system → violation of hemodynamics

d) exotoxin release from the organ → damage to the epithelium of the renal tubules

e) organ sensitization to exotoxin → severe toxic and hyperergic forms of diphtheria

2) Clinical and anatomical forms:

a) diphtheria of the pharynx and tonsils

b) diphtheria of the upper respiratory tract:

true croup is croup inflammation of the larynx in diphtheria

descending croup is a widespread croup inflammation of small branches of the bronchial tree

3) Morphology of local changes:

a) diphtheria of the pharynx and tonsils - both local and systemic changes:

enlarged tonsils

full-blooded mucous membrane, covered with whitish-yellow dense films

swelling of the soft tissues of the neck, sometimes swelling up to the anterior surface of the chest

diphtheretic inflammation (necrosis of the upper layers of the epithelium, dense fibrinous overlays firmly associated with the underlying epithelium)

enlarged, full-blooded, with foci of yellowish-white necrosis and hemorrhage, regional neck

b) diphtheria of the upper respiratory tract - only local changes are characteristic:

croup inflammation of the larynx, trachea, bronchi with easily departing fibrinous films, which are released in the form of casts when coughing

copious mucus secretion (prevents toxinemia)

4) Morphology of general changes:

a) heart: toxic myocarditis (1) alterative 2) interstitial)

expansion of the heart cavities in diameter

dull, flabby, mottled on the incision, often with parietal myocardial thrombi

edema, fullness of blood, cellular infiltration of interstitium

Issue: 1) early paralysis of the heart in diphtheria (death from OSN at the beginning of the 2nd week)

2) cardiosclerosis

b) the nervous system:

damage to the peripheral nerves and ganglia located closest to the pharynx

parenchymal neuritis with myelin breakdown

dystrophy of nerve cells up to cytolysis in nerve ganglia

Issue: 1) late paralysis of the soft palate, diaphragm, and heart (after 1.5-2 months) 2) regeneration of PNS elements

c) adrenal medulla: hemorrhages, dystrophy, cell necrosis; cortical layer: necrosis, disappearance of lipids

d) kidneys: necrotic nephrosis, massive necrosis of the cortical layer

e) spleen: pulp fullness, hyperplasia of B-follicles with pronounced karyorexis in follicle reproduction centers

5) Complications : the occurrence of pressure sores during tracheal intubation → purulent perichondritis of laryngeal cartilage, phlegmon, purulent mediasthenitis.

Causes of death in:

a) diphtheria of the pharynx and tonsils:

early cardiac paralysis in myocarditis

late paralysis of the heart or diaphragm in parenchymal neuritis

b) diphtheria of the upper respiratory tract:

asphyxia (true croup or blockage of the respiratory tract by fibrinous films)

secondary pneumonia, purulent complications